It is known to absorb gaseous constituents from a gas phase using conventional contact techniques and conventional contact equipment, such as packed columns.
However, this technique has the disadvantage in that it is possible to operate only within a restricted range of gas/liquid flow rate ratios because otherwise operational problems occur, such as, for example, "flooding" or the entrainment of liquid. The consequence of this is, in particular, that when removing components at low concentration levels it is necessary to work outside the optimum operating conditions of the equipment used (gas/liquid ratio 100:1-1:100) and/or with a liquid flow rate higher that is strictly necessary, in order to obtain an optimum loading and/or in order to be able to remove the components effectively.
Said known techniques are therefore not suitable for the removal of gaseous impurities which are present in low to very low concentrations (i.e. below 1 mg/m.sup.3). Even in those cases where the gaseous impurities can be removed by means of the conventional absorption techniques, said techniques will not be cost-effective or will be barely cost-effective because of the high liquid flow rates required.
Furthermore, in the case of said known contact techniques absorption usually proceeds via an acid/base reaction, as a result of which the field of application is restricted to gaseous constituents which can be absorbed via a mechanism of this type. The use of redox reactions in the absorption of gaseous constituents has not been described to date.